Pat the chicken thighs dry with paper towels to remove excess moisture for crispier skin.
In a small bowl, mix together kosher salt, black pepper, garlic powder, and smoked paprika.
Rub the chicken thighs all over with olive oil, then evenly season both sides with the spice mixture.
Preheat the air fryer to 400°F (200°C) for 5 minutes.
Place the chicken thighs skin side down in a single layer in the air fryer basket. Do not overcrowd.
Cook for 10 minutes at 400°F (200°C).
Flip the chicken thighs so the skin side is up, then cook for an additional 12 minutes or until the internal temperature reaches 165°F (74°C) and the skin is crispy.
Remove the chicken thighs from the air fryer and let rest for 5 minutes before serving.